Pcct apparatus and control method thereof

Abstract

Provided are a PCCT apparatus and a control method thereof capable of improving correction accuracy of a projection value even in a range in which the projection value is smaller. A PCCT apparatus includes a scanner that rotates an X-ray source which irradiates a subject with X-rays and a photon counting detector which detects X-rays transmitted through the subject for each of a plurality of energy bins, around the subject, an image generation unit that generates a tomographic image by using projection data calculated based on an output of the photon counting detector, and a controller that controls each unit, in which the controller calculates a conversion expression for converting a projection value of the subject into a transmission length by using a plurality of projection values acquired by performing rotational imaging on a phantom which is disposed not to overlap a rotation center of the scanner and of which a material, a shape, and a size are known, along with a plurality of transmission lengths of the phantom.

What is claimed is: 
     
         1 . A PCCT apparatus comprising:
 a scanner that rotates an X-ray source which irradiates a subject with X-rays and a photon counting detector which detects X-rays transmitted through the subject for each of a plurality of energy bins, around the subject;   an image generation unit that generates a tomographic image by using projection data calculated based on an output of the photon counting detector; and   a controller that controls each unit,   wherein the controller calculates a conversion expression for converting a projection value of the subject into a transmission length by using a plurality of projection values acquired by performing rotational imaging on a phantom which is disposed not to overlap a rotation center of the scanner and of which a material, a shape, and a size are known, along with a plurality of transmission lengths of the phantom.   
     
     
         2 . The PCCT apparatus according to  claim 1 ,
 wherein a cross-sectional shape of the phantom is a polygonal shape having an acute internal angle.   
     
     
         3 . The PCCT apparatus according to  claim 2 ,
 wherein a vertex of the acute internal angle of the phantom is disposed in a vicinity of the rotation center of the scanner.   
     
     
         4 . The PCCT apparatus according to  claim 1 ,
 wherein, in a case where the phantom is placed on a top plate, a projection value including the top plate is not used to calculate the conversion expression.   
     
     
         5 . The PCCT apparatus according to  claim 1 ,
 wherein the controller calculates a position of the phantom by using projection data of the phantom, prior to obtaining the transmission length of the phantom.   
     
     
         6 . The PCCT apparatus according to  claim 1 ,
 wherein the controller calculates a position of the phantom by using a tomographic image generated from projection data of the phantom, prior to obtaining the transmission length of the phantom.   
     
     
         7 . A control method of a PCCT apparatus including a scanner that rotates an X-ray source which irradiates a subject with X-rays and a photon counting detector which detects X-rays transmitted through the subject for each of a plurality of energy bins, around the subject, and an image generation unit that generates a tomographic image by using projection data calculated based on an output of the photon counting detector, the control method comprising:
 calculating a conversion expression for converting a projection value of the subject into a transmission length by using a plurality of projection values acquired by performing rotational imaging on a phantom which is disposed not to overlap a rotation center of the scanner and of which a material, a shape, and a size are known, along with a plurality of transmission lengths of the phantom.